Cancer now ranks at the top of causes of death and this tendency seems to last much longer. Thus, many attempts have been made to develop medicaments for curing the cancer and many researchers have engaged in studies to extract anti-tumor components from plants for a long time. For analogs of cyclic hexapeptide compounds including N-methyltyrosine and alanine of the present invention, RA-VII (TPC-B; JP-A-58-21655), RA-V (Chem. Pharm. Bull., 32, 284-290, 1984), etc., which are extracts from Rubiaceae herbs, a kind of medicinal plants, are known, among which RA-VII has been regarded as promising, but has been found not fully effective yet.
An object of the present invention is to provide a cyclic hexapeptide compound having a superior pharmaceutical effect than RA-VII.